Differentials = Balls (are gear diff gone forever?)

[chb]

Re-staring RC, and gearing up, I met only cars with ball differentials...

What I don't like about them, is the requirement for maintenance

My first question(race) is : The advantage over gear differentials is only the ability to reduce freedom (by tightening). We could envisage the same with gears after all : very high viscosity grease(coarse adjustement) and slight tightening(fine adjustemen). Do you agree with that ?

Second question(play): for bashing around with insane motor power, ball differentials become the real weakness. Can some cars be fitted with gear differentials(I mean not toys, real cars like B44/B4, BJ4, zx5/RB5, D4, ...) ?

Thanks!

[thom.p]

AE are coming out with the new SC10 and it comes with an gear diff.
So you can run an gear diff in a T4/B4.

[RogerM]

Firstly I get about 4-6 months out of my diffs before they need attention, stock Kyosho parts but with Kyosho Ceramic main diff balls.

On top of that the ability to make an adjustment without having to strip the car down makes the ball diff a huge tuning aid. Also they are MUCH lighter which improves throttle response etc.

As for bashing you can just tighten them up a bit and set the slipper a bit tighter then back them off when you go racing and handling becomes the main focus again.

[Lee Martin]

SC10 gear diff is the same weight as the Ball diff.........

[super__dan]

Is it a direct fit into a B4 gearbox Pidge?

[Lee Martin]

nope, you will need to order the SC10 gear box housing and rear plate, i think thats the only other parts you will need....

[Neil Skull]

Originally Posted by chb

Re-staring RC, and gearing up, I met only cars with ball differentials...

What I don't like about them, is the requirement for maintenance

My first question(race) is : The advantage over gear differentials is only the ability to reduce freedom (by tightening). We could envisage the same with gears after all : very high viscosity grease(coarse adjustement) and slight tightening(fine adjustemen). Do you agree with that ?

Second question(play): for bashing around with insane motor power, ball differentials become the real weakness. Can some cars be fitted with gear differentials(I mean not toys, real cars like B44/B4, BJ4, zx5/RB5, D4, ...) ?

Thanks!

I use a 4.5 turn in a TC with 2 diffs no problem.
If you want geared diffs with electric offroad then how about 1/8th electric class.

[Richard Lowe]

Originally Posted by Neil Skull

I use a 4.5 turn in a TC with 2 diffs no problem.
If you want geared diffs with electric offroad then how about 1/8th electric class.

Remember with smaller wheels there's much less stress on the diff...

[SlowOne]

Originally Posted by Richard Lowe

Remember with smaller wheels there's much less stress on the diff...

Er... not quite! Stress on the diff is a function of the torque the diff has to transmit, and the weight of the car, not the size of the wheels. In off-road, there is so little grip compared to TC that the diffs take less of bashing.

As Warped says, the main stress that an Off Road diff takes is the constant shock loads of the car skipping across the terrain, and the wheels spinning up and then gripping again. What amazes me is the abuse an off-road diff will take before it cries "enough!" In a TC, it is the large amounts of torque in quite a weighty car that shorten their life, and in off-road that isn't the case. Wheel diameter is just a reflection of gearing, not load.

Either way, a geared diff is going to be much stronger from a life point of view, but will need more work to tune. However, once oyu have the space for a geared diff, you have the space for a Torsen diff - and they are awesome!

[Lee]

Originally Posted by SlowOne

Er... not quite! Stress on the diff is a function of the torque the diff has to transmit, and the weight of the car, not the size of the wheels. In off-road, there is so little grip compared to TC that the diffs take less of bashing.

As Warped says, the main stress that an Off Road diff takes is the constant shock loads of the car skipping across the terrain, and the wheels spinning up and then gripping again. What amazes me is the abuse an off-road diff will take before it cries "enough!" In a TC, it is the large amounts of torque in quite a weighty car that shorten their life, and in off-road that isn't the case. Wheel diameter is just a reflection of gearing, not load.

Either way, a geared diff is going to be much stronger from a life point of view, but will need more work to tune. However, once oyu have the space for a geared diff, you have the space for a Torsen diff - and they are awesome!

Sorry but i have never seen a TC wheelie, where as i know numerous 4wd's that you can flip on grass. I remember from TC that they would spin the wheels up on the line, this is not the case with off road unless its wet or on dirt

[Chris Doughty]

typical 'UK' off-road - dry astro turf with yellow mini-spikes is incredibly 'bitey'

xxx-s plastic outdrives can be had for lunch in the xxx-4

so could the xxx-s front spool in a xxx-4

and blowing xxx-s one-ways in the front of a xxx-4 was considered normal.

all of these items lasted (at least for 5 minutes) in the xxx-s

[Richard Lowe]

Originally Posted by SlowOne

Er... not quite! Stress on the diff is a function of the torque the diff has to transmit, and the weight of the car, not the size of the wheels. In off-road, there is so little grip compared to TC that the diffs take less of bashing.

With larger diameter wheels the diff is spinning slower for the same ground speed. As power is 'torque x RPM', given the diff is spinning more slowly to give equal power transfered the torque must be higher

[MHeadling]

So what effect will a gear diff have on a 2wd and 4wd?

I had a gear diff in my Serpent S400 TC, was good as far as maintence was concerned but it used to kick the rear end out under hard acceleration due to no slip.

[warped]

Diffs in a touring car have an easy time of things.
Small wheels and no bumps or jumps mean they have to deal with far less torque, and much lower shock loadings.

Was wondering if kyosho do a geared diff that fit's the ZX5 gearbox, myself. - Maybe something from one of their nitro cars.

I'm also reckon that a bit of mass in the transmission could be quite useful.

I'm sure that was one of the main reasons losi Hydradrives made the car so smooth to drive.

[chb]

Originally Posted by warped

Diffs in a touring car have an easy time of things.
Small wheels and no bumps or jumps mean they have to deal with far less torque, and much lower shock loadings.

Was wondering if kyosho do a geared diff that fit's the ZX5 gearbox, myself. - Maybe something from one of their nitro cars.

Good point... Actually the ZX5 being also a RTR/cheap platform, I would expect some gear diiff in the RTR ?

[RogerM]

ZX5 RTR uses the same basic diff design as the rest of the ZX5 series

[Alex H]

Losi xxx-cr can also use gear diff. One guy up here in the north has modified his and it works fine.